MATERIAL TRANSFORMATIONS IN THE PLANT 



175 



germination in darkness stored substances alone are utilized, the chemical 

 nature and amount of which can be determined by exact analysis. Quite 

 similar phenomena occur also in plants growing in light; but matters are com- 

 plicated in this case by the fact that the process is accompanied by the assimila- 

 tion of carbon dioxide and mineral constituents. This assimilation results in 

 the formation of new substances, of external origin, which obscure the trans- 

 formations occurring in the reserve materials. By studjdng germination in 

 darkness and in distilled water we may eliminate the absorption of all materials 

 fexcept water and atmospheric oxygen, and may thus study the changes of re- 

 serve materials abeady within the plant. 



It is generally observed that the dry weight of seedlings of various plants is 

 considerably less than the dry weight of the ungerminated seeds. This is illus- 

 trated by the following analyses of 46 wheat seeds and of the same number of 

 seedlings. The numbers represent grams. 



The chemical processes of germination are not identical in different kinds 

 of seeds; they depend largely upon the chemical nature of the stored reserve 

 materials. Seeds are grouped into three classes according to the nature of 

 the reserve materials that predominate in them, starchy seeds, proteinaceous 

 seeds and fatty seeds. 



From the table given above it is evident that the loss of material during the 

 germination of starchy seeds (such as those of the Graminese^) occurs through 

 loss of carbon, oxygen and hydrogen. The amount of nitrogen and of ash con- 

 stituents remains unchanged. The nature of the transformations occurr'ing in 

 the germination of maize is shown in the following table, which presents the re- 

 sults of analyses of 22 maize seeds and of as many seedlings. The numbers 

 represent grams. It thus appears that most of the starch is decomposed by 

 diastase, with the formation of glucose and cellulose. 



I Boussingault, 1860-1891. [See note S, p. 2.I Vol- 4. 



